Many different kinds of display and writing slates have been developed for various uses, including personal drawing and writing, blackboard-type presentations, games, etc. Slates have ranged from simple erasable chalkboards to various kinds of high-tech devices.
A few devices which might be characterized as slates have even utilized the light-modulating characteristics of liquid crystals to allow creation of images. Liquid crystal display devices, which are well known, depend, of course, upon the re-orientation of the liquid crystals in the presence of a field (for example, an electric field) to change visual characteristics or otherwise serve their purpose.
Such liquid crystal displays commonly employ spaced conductive lattice networks, single conductive planes with spaced conductive lattice networks, or pairs of conductive planes. Such arrangements have liquid crystal material between conductive networks and/or planes to apply the fields which create reorientation and the resulting images in the liquid crystal material.
Some devices of this type include those disclosed in U.S. Pat. Nos. 4,814,760 (Johnston et al.), U.S. Pat. No. 3,781,085 (Liebowitz), U.S. Pat. No. 4,685,770 (Baeger), U.S. Pat. No. 4,525,032 (Hilsum), and U.S. Pat. No. 3,947,183 (Haas et al.).
Some of such slates are equipped with writing instruments intended to change the polarization of a liquid crystal. However, devices of the prior art have a number of shortcomings and/or disadvantages when considered as writing/drawing slates for various purposes.
In some devices, it is not possible to obtain a solid continuous line. Some devices are very complex and expensive in construction and do not lend themselves to wide usage for writing/drawing usage, classroom usage, toy or game uses, or the like. Some, because of how they function, may unnecessarily limit the creative skills of the user; because they are point-, line-, or area-limited, they do not lend themselves to creation of artistic images, for example, of the type possible with devices such as brushes, pads, or even fingers of the hand.
Yet another disadvantage of certain devices of the prior art is the inability of such devices to hold an image for a sufficient duration. Liquid crystal images after removal of a potential-applying means tend to be fleeting. In addition, certain prior devices do not have simple, easily usable erasing means, for example, similar to blackboard erasers. Instead, erasing can be time-consuming.
A variety of light-modulating liquid crystal products have been made utilizing LC-layers which have a polymeric material forming and holding micro-volumes of liquid crystal material. However, LC-layers of this type have heretofore not been successfully utilized in simple slate products of the writing/drawing type.
An easily-erasable liquid crystal writing/drawing slate, which has great versatility in image creation, good image retention, and easy erasibility, and which is easily usable and inexpensive in construction would be an important advance in the art.